The present invention relates generally to batteries, and more particularly to opening-sealing devices of organic electrolytic batteries.
Recently, in accordance with considerable progress being made in electronic fields, improvement for primary batteries which are used as power sources for the electronic equipment is being made in terms of size-reduction, weight-reduction, high energy density and high reliability. As one example of primary batteries for the electronic equipment is known an organic electrolytic battery in which a lithium alloy such as lithium and lithium-aluminum (Li-Al) alloy is used as the negative electrode active material, an aprotic nonaqueous electrolyte with a high relative permittivity and a low viscosity is used as the electrolyte, and a graphite fluoride or metallic oxide such as manganese dioxide and copper oxide is used as the positive electrode active material. In the case of operating this primary battery for a long time, the opening-sealing is required to have an extremely high airtightness. If charging is made in the battery due to internal short-circuit or leakage current, gases are generated in the battery and the gas generation provides the possibility that the pressure in the battery abnormally increases to cause explosion of the battery. Thus, in order to prevent the battery explosion, there is provided a battery opening-sealing device with a valve which is constructed by a single metallic thin plate or a composite member comprising a metal plate and a synthetic resin film as disclosed in the Japanese Utility Model Publication No. 59-15398, Japanese Utility Model Provisional Publication No. 53-40433 or U.S. Pat. No. 3062910. Thereafter, as a result of improvement made for this battery opening-sealing device for practical application purposes, there is provided a dish-like opening-sealing plate with a valve which comprises a three-layer lamination film device including a metallic thin film expanded in accordance with increase in the pressure in the battery or broken by the gas pressure in the battery and head-adhesion type resin films provided at both surfaces of the metallic thin film to protect the metallic thin film against the electrolyte and corrosive gases in the atmosphere. The above-described opening-sealing plate is constructed in accordance with the following steps:
1) installing the valve on the inner bottom surface of the opening-sealing plate;
2) mounting a terminal cap (reinforcing plate) on the upper surface of the valve;
3) pressing the circumferential portion of the terminal cap by a jig heated up to above the fusing point of the heat-adhesion type resin film, so that the valve is fixedly heat-adhered to both the circumferential portion of the terminal cap and the inner bottom surface of the dish-like opening-sealing plate;
4) bending a circumferential portion of the dish-like opening-sealing plate inwardly by means of a jig until the circumferential portion thereof is directed to the horizontal directions, thereby fixing the circumferential portion of the terminal cap; and
5) inserting the opening-sealing plate into an annular insulating packing member whose cross section substantially has a L-configuration.
However, according to this machining process, in the step 4), delicate care is necessary in terms of the following points. That is, as illustrated in FIG. 1, the rising portion 1b of the circumference of the dish-like opening-sealing plate 1 is inserted into a jig X having a predetermined inner diameter and a predetermined configuration to reach an arc portion R through a linear portion X1 so as to be bent horizontally to be surely calked with respect to a reinforcing plate 4 as indicated by a dotted line, thereby having a diameter substantially equal to the inner diameter of the jig X and a circumferential configuration corresponding to the shape of the arc portion R of the jig X. Illustrated at character Y is a jig for supporting the dish-like opening-sealing plate 1 and illustrated at character Z is a jig for fixedly pressing and holding the reinforcing plate 4. In this case, since the top portion le of the rising portion 1b of the circumference of the dish-like opening-sealing plate 1 has an edge-like configuration, a considerable high frictional force generates at the connecting point between the arc portion R and the linear portion X1 when calking, so that a force F1 is applied to the rising portion 1b so as to be pressed downwardly. This force Fl varies in accordance with the differences of the machining accuracies (dimension error) for the inner diameter of the jig X and the outer diameter of the dish-like opening-sealing plate 1, the machining accuracy of the rising portion 1b and others. This force F1 produces a force F2 which results in the fact that a horizontal portion 1c of the dish-like opening-sealing plate 1 is pressed upwardly, whereby the horizontal portion 1c thereof is deformed so as to form an inclined portion as indicated by a dotted line in FIG. 2. The deformation of the horizontal portion 1c of the dish-like opening-sealing plate 1 causes a load to be applied to the valve 3 and others processed in the previous step 3). In this case, since the valve and reinforcing plate 4 are in the strongly heat-adhered conditions, the load acts so as to separate the valve 3 from the opening-sealing plate portion 1c so as to form a gap as illustrated in FIG. 3. As a result, there is a problem that the formed gap allows the electrolyte in the battery to reach the upper surface of the terminal cap (reinforcing plate 4).